Ligand- and voltage-activated currents have been studied in primary cultured rat DRG (sensory) neurons and a putative rat sensory neuron cell line, F11, using the patch-electrode voltage clamp technique. Pain- inducing peptide - i.e., bradykinin, and non-peptide pain-inducing agents - e.g., capsaicin and reciniferatoxin have been applied to voltage-clamped sensory neurons and their receptor-activated currents and effects on voltage-dependent ionic currents have been analyzed. We have observed that in addition to receptor-activated current flows by these agents, these agents also modulate voltage-dependent ion channel activities. Low concentrations of these agents stimulate enhancement of both low-and high-threshold Ca currents as well as a voltage-dependent Na current. Higher concentrations of these agents show either biphasic effect (initial enhancement followed by depression) or simply depress these ionic currents. While the primary cultured DRG neurons and Fll cells are similar in membrane properties, the latter cell line was found to be too unstable to serve as a sensory neuron model.